The confederation has succeeded in establishing a new country. However, the residents of each state still tended to think of themselves as citizens of their particular state rather than as Americans. Under the Articles, many of the states continued to have only limited contact with each other. This made it difficult for them to agree on the common interests and goals for the government.
Random changes in allele frequency in a population are usually called genetic drift. The reason why this is the answer is because it is a very specific word which is used to describe exactly that - random changes in allele frequency.
All the other cases; answers, here aren't correct and don't apply.
